Easy-fit heat screening device for connecting a cooling pipe and a through-hole formed in a nozzle support ring of a gas turbine

ABSTRACT

An easy-fit heat screening device ( 110 ) for connecting a cooling pipe ( 112 ) and a through-hole ( 114 ) formed in a nozzle support ring ( 116 ) of a gas turbine, of the type comprising a tubular structure ( 118 ) which has an external diameter smaller than a diameter of the through-hole ( 114 ) and into which the cooling pipe ( 112 ) extends; this tubular structure ( 118 ) has at the top a shaped annular end ( 126 ) which is inserted inside a groove ( 130 ) formed in the through-hole ( 114 ).

[0001] The present invention refers to an easy-fit heat screening devicefor connecting a cooling pipe and a through-hole formed in a nozzlesupport ring of a gas turbine.

[0002] As is known, gas turbines are machines consisting of a compressorand single or multiple-stage turbine, where these components areconnected together by a rotating shaft and where a combustion chamber isprovided between the compressor and the turbine.

[0003] In these machines, air from the external environment is suppliedto the compressor so as to pressurise it.

[0004] The pressurised air passes through a series of pre-mixingchambers which terminate in a converging portion and inside each ofwhich an injector feeds the fuel which is mixed with the air so as toform an air/burning fuel mixture.

[0005] The fuel is introduced inside the combustion chamber and isignited by means of suitable sparking plugs so as to produce combustionwhich is aimed at causing an increase in temperature and pressure andtherefore enthalpy of the gas.

[0006] At the same time, the compressor supplies pressurised air whichis made to pass both through the burners and through the casing of thecombustion chamber so that the abovementioned pressurised air isavailable for fuelling the combustion.

[0007] Then the high-temperature and high-pressure gas reaches, viasuitable ducts, the different stages of the turbine which converts theenthalpy of the gas into mechanical energy which is available to theuser.

[0008] It is known, moreover, that in order to achieve the maximumefficiency of a given gas turbine it is necessary for the temperature ofthe gas to be as high as possible; however, the maximum temperaturevalues which can be reached during use of the turbine are limited by thestrength of the materials used.

[0009] Furthermore, in gas turbines, as in other turbine machines, it isnecessary to prevent these hot gases from being drawn into spaces whichare situated around the impellers of the said turbines.

[0010] It is therefore necessary to pressurise suitably the cavitieswhich are adjacent to the fluid path so as to prevent a reduction in theefficiency and excessively high operating temperatures of the turbineimpellers.

[0011] In the known art, cooling pipes are used for this purpose, saidpipes conveying a cooling air which is supplied from the compressor andhaving, for example, to pass through the nozzles of the firstlow-pressure stage (which are thus provided with suitable holes) andthrough the nozzle support ring, in order to reach the zones to bepressurised.

[0012] In particular, the air which is tapped from the compressor has atemperature which is considerably lower than the operating temperatureof the nozzle support ring. In order to avoid—in the zones where thecooling pipes pass through a through-hole formed in the nozzle supportring—the spread of high temperatures inside the said support ring, heatscreening devices have been introduced.

[0013] These devices are arranged between the cooling pipe and thethrough-hole of the nozzle support ring and comprise a tubularstructure.

[0014] It is pointed out, moreover, that these tubular structures alsoperform another function. In fact they act as a seat for the coolingpipe and ensure a sealed connection with the through-hole formed in thenozzle support ring.

[0015] The cooling pipe, which generally has spherical ends, departsfrom an external casing of the turbine and terminates inside thethrough-hole of the nozzle support ring.

[0016] In some types of gas turbine, the seat for the spherical end ofthe cooling pipe is provided by a bush inserted from the outside of thenozzle support ring and locked with a ring nut on the inside of the ringitself. This is possible when the through-holes passing through thenozzle support ring are straight, there being only one zone wherepressurisation is to be performed.

[0017] In gas turbines, however, where there are two zones to besupplied, the through-holes passing through the nozzle support ring areof two types: one which is straight and the other inclined. In thiscase, in the prior art, two different types of fixing devices are used,one for straight holes and one for inclined holes, using also twodifferent fixing methods.

[0018] The object of the present invention is therefore that ofovercoming the abovementioned drawbacks and in particular that ofproviding an easy-fit heat screening device for connecting a coolingpipe and a through-hole formed in a nozzle support ring of a gas turbinewhich can be applied equally well to straight holes and inclined holes.

[0019] Another object of the present invention is that of providing aneasy-fit heat screening device for connecting a cooling pipe and athrough-hole formed in an nozzle support ring of a gas turbine whichallows a reduction in production and maintenance costs compared to theprior art.

[0020] Another object of the present invention is that of providing aneasy-fit heat screening device for connecting a cooling pipe and athrough-hole formed in a nozzle support ring of a gas turbine which isparticularly reliable, simple and functional.

[0021] These and other objects according to the present invention areachieved by providing an easy-fit heat screening device for connecting acooling pipe and a through-hole formed in a nozzle support ring of a gasturbine as described in claim 1.

[0022] Further characteristic features are described in the claims whichfollow.

[0023] The characteristic features and advantages of an easy-fit heatscreening device for connecting a cooling pipe and a through-hole formedin a nozzle support ring of a gas turbine according to the presentinvention will emerge more clearly and fully from the followingdescription provided by way of a non-limiting example with reference tothe accompanying schematic drawings in which:

[0024]FIG. 1 is a cut-away side elevation view of a connection between acooling pipe and a straight through-hole formed in a nozzle support ringof a gas turbine, with a heat screening device according to the priorart inserted therein;

[0025]FIG. 2 shows a sectioned side elevation view of a connectionbetween a cooling pipe and a through-hole, having two inclined sectionsformed in a nozzle support ring of a gas turbine, in one section therebeing inserted an easy-fit heat screening device according to thepresent invention;

[0026]FIG. 3 shows a sectioned side elevation view of a connectionbetween a cooling pipe and a straight through-hole formed in a nozzlesupport ring of a gas turbine, where a system for fixing a heatscreening device according to the present invention using a mountingtool is shown;

[0027]FIG. 4 shows an enlarged view of FIG. 3 illustrating a top end ofthe heat screening device according to the present invention, after useof a mounting tool;

[0028]FIG. 5 shows an enlarged view of FIG. 3 illustrating a top end ofthe heat screening device according to the present invention, before useof a mounting tool.

[0029] With reference to FIG. 1, a heat screening device according tothe prior art is indicated overall by 10, said device being intended tojoin together a cooling pipe 12 and straight through-hole 14 formed in anozzle support ring 16 of a gas turbine.

[0030] In the example according to FIG. 1, the screening device 10comprises a tubular structure 18 having a top end 20 with an externaldiameter approximately equal to an internal diameter of the through-hole14.

[0031] This tubular structure 18 is inserted from the outside of thenozzle support ring 16 and is arranged at a bottom end of thethrough-hole 14, being locked there by a ring nut 22 mounted on theinside of the said ring 16 so as to support the overlying tubularstructure 18.

[0032] A bottom—generally spherical—end of the cooling pipe 12 extendsinside the tubular structure 18.

[0033]FIGS. 2, 3, 4 and 5 illustrate an easy-fit heat screening device110, according to the present invention, for connecting a cooling pipe112 and a through-hole 114 formed in a nozzle support ring 116 of a gasturbine, where components identical/or equivalent to those illustratedin FIG. 1 have the same reference numbers increased of 100.

[0034] More precisely, FIG. 2 shows a through-hole 114 having twosections inclined with respect to each other, whereas FIG. 3 shows astraight through-hole 114.

[0035] In both cases and as can be clearly seen in FIG. 5, an upper zoneof the through-hole 114 has a groove 130. The groove 130 is defined atthe bottom by a first flat surface 132 which is substantiallyperpendicular to the axis of this upper zone and at the top by a secondflat surface 134 having an inclination along a line directed towards anouter extension of the first surface 132.

[0036] The upper zone of the through-hole 114 has, above the groove 130,a first internal diameter greater than a second internal diameterprovided underneath the said groove 130.

[0037] The screening device 110 comprises a tubular structure 118. Thistubular structure 118 is inserted from the outside of the nozzle supportring 116 and is arranged inside the through-hole 114.

[0038] The tubular structure 118 has at the bottom an annular end 124with an external diameter which is approximately equal to the secondinternal diameter of the through-hole 114.

[0039] At the top, the tubular structure 118 has a shaped annular end126.

[0040] As can be clearly seen in FIG. 5, an external surface of theshaped annular end 126 is formed with two different diameters. At thetop a first external cylindrical surface 128 is provided, said surfacehaving a diameter slightly smaller than the first internal diameter ofthe through-hole 114. At the bottom there is a second externalcylindrical surface 129, with a diameter slightly smaller than thesecond internal diameter of the through-hole 114.

[0041] The first external cylindrical surface 128 is joined to thesecond external cylindrical surface 129 by a flat annular surface 127which extends substantially perpendicularly with respect to the axis ofthe upper zone of the through-hole 114.

[0042] Finally, the shaped annular end 126 terminates at the top in aflat surface 125, having an inclination along a line directed towards anouter extension of the flat annular surface 127.

[0043] A bottom—generally spherical—end of the cooling pipe 112 extendsinside the tubular structure 118.

[0044] The operating principle of the easy-fit heat screening device 110for connecting a cooling pipe 112 and a through-hole 114 formed in anozzle support ring 116 of a gas turbine, according to the presentinvention, is clear from that described above with reference to thefigures and briefly is as follows.

[0045] The heat screening device 110 is inserted, from outside of thenozzle support ring 116, into the upper zone of the through-hole 114.Insertion is performed so that the flat annular surface 127 mates withthe first flat surface 132 of the groove 130.

[0046] At this point, in order to lock the heat screening device 110inside the through-hole 114, the shaped annular end 126 is engagedinside the groove 130.

[0047] More precisely, the shaped annular end 126 is bent, as can beseen in FIG. 3, using for example a mounting tool with a conical endwhich is inserted from the outside of the nozzle support ring 116.

[0048] After this operation, as shown in FIG. 4, the shaped annular end126 enters partly inside the groove 130; in particular, the flat surface125 of the shaped annular end 126 engages in an interfering manner withpart of the second flat surface 134.

[0049] It is clear that the first external cylindrical surface 128 isdesigned with dimensions suitable for this purpose: the inclination ofthe second flat surface 134 is also approximately parallel to theinclination of the flat surface 125 of the shaped annular end 126 suchthat, after bending of the shaped annular end 126, the flat surface 125makes firm contact with the second flat surface 134.

[0050] The heat screening device 110 advantageously uses anoil-hydraulic apparatus equipped with the conical-end mounting tool andable to generate a thrust, for example, of 10,000 Newton.

[0051] It should be noted how, in order to lock the device 110, it isnecessary to act exclusively on the outside of the nozzle support ring116.

[0052] It must also be pointed out how the material from which the heatscreening device 110 according to the invention is made must have, inaddition to heat resistance characteristics, also good plasticdeformation properties required for bending of the shaped annular end126.

[0053] The description provided clearly illustrates the characteristicfeatures of the easy-fit heat screening device for connecting a coolingpipe and a through-hole formed in a nozzle support ring of a gas turbineaccording to the present invention, as well as the advantages associatedtherewith, including:

[0054] simple installation and maintenance;

[0055] reliability;

[0056] lower costs, compared to the prior art, since there is a singleheat screening device suitable for both a straight cooling pipe and apipe with two sections inclined relative to each other: the reduction inthe costs arises from the fact that use of the device according to theinvention, although it requires a special tool, is industrially moresimple than the prior art where it was required to perform a finalsafety spot weld.

[0057] Finally, it is clear that the easy-fit heat screening device forconnecting a cooling pipe and a through-hole formed in a nozzle supportring of a gas turbine thus conceived may be subject to numerousmodifications and variants, all of which fall within the scope of theinvention; moreover, all the details may be replaced by technicallyequivalent elements. In practice the materials used, as well as theforms and the dimensions may be of any nature according to the technicalrequirements.

[0058] The scope of protection is therefore defined by the accompanyingclaims.

1. An easy-fit heat screening device (110) for connecting a cooling pipe (112) and a through-hole (114) formed in a nozzle support ring (116) of a gas turbine, of the type comprising a tubular structure (118) which has an external diameter smaller than a diameter of said through-hole (114) and into which said cooling pipe (112) extends, characterized in that said tubular structure (118) has at the top a shaped annular end (126) which is inserted inside a groove (130) formed in said through-hole (114).
 2. Heat screening device (110) according to claim 1, characterized in that said insertion is performed by means of bending of said shaped annular end (126).
 3. Heat screening device (110) according to claim 2, characterized in that said insertion is performed by means of interference between said shaped annular end (126) and said groove (130).
 4. Heat screening device (110) according to claim 3, characterized in that said groove (130) is formed in an upper zone of said through-hole (114), said groove (130) being defined at the bottom by a first flat surface (132) and at the top by a second flat surface (134), with an inclination along a line directed towards an outer extension of said first flat surface (132).
 5. Heat screening device (110) according to claim 4, characterized in that said first flat surface (132) is substantially perpendicular to the axis of said upper zone of said through-hole (114), said upper zone of said through-hole (114) having, above said groove (130), a first internal diameter which is greater than a second internal diameter provided underneath said groove (130).
 6. Heat screening device (110) according to claim 5, characterized in that an external surface of said shaped annular end (126) is formed with two different diameters, at the top there being provided a first external cylindrical surface (128), with a diameter slightly smaller than said first internal diameter of said through-hole (114), and at the bottom there being a second external cylindrical surface (129), with a diameter slightly smaller than said second internal diameter of said through-hole (114).
 7. Heat screening device (110) according to claim 6, characterized in that said first external cylindrical surface (128) is joined to said second external cylindrical surface (129) by a flat annular surface (127) which extends substantially perpendicularly with respect to the axis of said upper zone of said through-hole (114).
 8. Heat screening device (110) according to claim 7, characterized in that said shaped annular end (126) terminates at the top in a flat surface (125) with an inclination along a line directed towards an outer extension of said flat annular surface (127).
 9. Heat screening device (110) according to claim 8, characterized in that it is inserted, from the outside of said nozzle support ring (116), into said upper zone of the through-hole (114), insertion being performed so that said flat annular surface (127) mates with said first flat surface (132) of said groove (130).
 10. Heat screening device (110) according to claim 2, characterized in that said shaped annular end (126) is bent using a mounting tool with conical ends which is inserted from the outside of said nozzle support ring (116).
 11. Heat screening device (110) according to claim 8, characterized in that said flat surface (125) of said shaped annular end (126) engages in an interfering manner with part of said second flat surface (134) of said groove (130).
 12. Heat screening device (110) according to claim 11, characterized in that the inclination of said second flat surface (134) is approximately parallel to the inclination of said flat surface (125) of said shaped annular end (126) such that, after bending of the shaped annular end (126), said flat surface (125) makes firm contact with said second flat surface (134).
 13. Heat screening device (110) according to claim 10, characterized in that said mounting tool is mounted on an oil-hydraulic apparatus.
 14. Heat screening device (110) according to Clam 5, characterized in that said tubular structure (118) has at the bottom an annular end (124) with an external diameter which is approximately equal to said second internal diameter of said through-hole (114).
 15. Heat screening device (110) according to claim 1, characterized in that said through-hole (114) is straight.
 16. Heat screening device (110) according to claim 1, characterized in that said through-hole (114) has two sections which are inclined with respect to each other.
 17. Heat screening device (110) according to claim 1, characterized in that a bottom end of said cooling pipe (112) is inserted inside said tubular structure (118).
 18. Heat screening device (110) according to claim 17, characterized in that said bottom end of said cooling pipe (112) is spherical.
 19. Easy-fit heat screening device (110) for connecting a cooling pipe (112) and a through-hole (114) formed in a nozzle support ring (116) of a gas turbine as substantially described and illustrated and for the purposes specified. 